1. Field
Embodiments relate to a control apparatus of a multi-finger hand of a robot, which has multiple fingers with multiple joints to grasp an object, and a grasping method using the same.
2. Description of the Related Art
Substantial research into robot fingers, which perform delicate operations like a human being, has conventionally been conducted. Particularly, much research into the location of tips of robot fingers at desired positions or the control of force applied to the tips to a desired degree has been conducted. Further, a multi-finger hand to stably grasp an object having a designated shape is now being researched.
Considerable research into grasping of an object by robot fingers is underway. In researching grasping of an object by robot fingers, a primary concern is how to stably grasp an object in a desired shape, i.e., a method of causing the robot fingers to approach the object such that the robot fingers smoothly grasp the object without inclination of the object.
In case of a multi-finger hand of a robot grasps an object, trajectory instructions of tips of respective fingers are input to a control apparatus, which considers a grasping state, calculates trajectories of the tips of the fingers and performs overall control of the multi-finger hand.
After positions of the tips of the respective fingers of the multi-finger hand are input to the control apparatus by the instructions, position instructions of the respective finger joints to grasp the object should be calculated and then input. Further, when the number of the fingers is increased, the number of the position instructions of the tips of the fingers to be input is increased. Moreover, when the multi-finger hand is moved, the number of variables to designate the motion is large and thus it is difficult to manipulate the multi-finger hand. For example, in the case where the multi-finger hand includes four fingers, each of which has three joints, twelve joint variables should be designated although simple joint angles are controlled. Further, in the case where the multi-finger hand grasps the object or moves or rotates the grasped object, it is necessary to simultaneously move the plural fingers in consideration of the relative motions of the respective fingers, and thus it is difficult to instruct an intuitive motion.
Therefore, it is recently assumed that there is a virtual object connected to the tips of the respective fingers of the multi-finger hand by virtual springs. Here, it is assumed that the virtual object is connected to a virtual desired object by a virtual spatial spring. Coordinates of the tips of the respective fingers of the multi-finger hand contacting the virtual object are defined, and the tips of the respective fingers move to a central position of the coordinates of the tips of the respective fingers, thereby achieving control of the grasping force of the object and manipulation of the multi-finger hand.
As described above, since the tips of the respective fingers move only to the central position of the coordinates of the tips of the respective fingers, there is a limit to achievement of various grasping methods, such as holding a cylindrical object with fingers and a palm or supporting of a flat object, such as a tray, on spread fingers.